Magnetic-disk drives generally utilize rotary actuators to position one or more magnetic read/write heads (also known as transducers) with respect to a similar number of magnetic disks rotatably mounted on a hub driven by a motor. The read/write heads are moved among particular tracks of the magnetic disk to gain access to the information recorded on that track and/or to write information to a particular location on the disk.
The read/write heads are mounted on an air bearing slider. The slider positions the read/write heads above the data surface of the disk by a cushion of air generated by the rotating disk. Alternatively, the slider may operate in contact with the surface of the disk. The slider is mounted to a suspension load beam or suspension arm assembly. The suspension arm maintains the read/write heads and the slider adjacent to or in contact with the data surface of the disk with as low a loading force as possible. The combination of the read/write heads, slider and suspension arm is sometimes referred to as the head gimbal assembly (HGA).
The suspension arm is connected to the distal end of a rotary actuator arm pivotally installed within the housing of the disk drive. A voice coil motor pivots the actuator arm to position the read/write heads over desired tracks at selected radii of the magnetic disks.
Currently, ball swaging is the preferred method of attachment of the suspension arm to the actuator arm. Generally, swaging is a process for connecting metallic components. The wall of a thin tubular component is expanded in compression against a complementary component wherein the thin tubular component experiences some degree of plastic deformation. More specifically, with respect to this invention, the process of swaging a suspension arm to an actuator arm involves pressing and fastening the periphery of a boss or sleeve of the suspension arm to the inner face or wall of a through-hole formed in the actuator arm. The boss or sleeve is typically integral with a mounting plate or baseplate attached to the suspension arm. To attach the suspension arm to the actuator arm, the boss is inserted into the through-hole formed in the actuator arm. Then, a swage ball having a diameter larger than the inner diameter of the opening of the boss is passed completely through the opening of the boss, forcing the boss against the inner wall of the through-hole. Depending upon the size of the swage ball relative to the through-hole, the inner wall defining the through-hole in the actuator arm will undergo a range of deformation from little to extensive. The swaging process generally provides a stronger connection than a press fit because the boss is work hardened by the deformation which actually increases tensile strength. Nevertheless, the deformation must be sufficient to reliably hold the separate pieces together. Unfortunately, the swage ball can tear away metal as it is forced through the through-hole and cause cracking and metal failure. The loose metal pieces may adhere to the perimeter of the exit side of the through-hole, like a metal burr, which may then dislodge after assembly of the drive, thereby placing metal debris on the surface of a disk. Such debris, if it breaks away, can cause extensive damage to the disk. Moreover, the quantity of the debris can increase if the pieces are plated, such as nickel-plated pieces. In addition, the swaging process can alter the attitude of the suspension, thereby changing the position of the slider relative to the disk in the final assembly. If the flying characteristics of the slider are changed as a result, the flying dynamics of the slider and the overall performance of the drive may be adversely affected. Thus, it can be seen that there is a need for a lubricant in the swaging process.
Deswaging is the process of disconnecting components that have been joined by swaging. It is often desirable to deswage components when a drive needs to be reworked, as in the case when testing reveals problems in operation or function of the disk drive. For example, testing may reveal that a transducer is not performing properly and needs replacing. In such a circumstance, it is desirable to deswage the suspension arm from the actuator arm and replace it with a new suspension arm, slider and transducer; however, it is desirable to re-use the original actuator arm.
As previously described, swaging is a severe process, particularly with nickel-plated metal actuators and suspension arms. The swaging process creates a retention torque between the mating metal pieces that must be overcome to separate or free the metal pieces from each other. As a result, deswaging of parts can cause damage to both the actuator arm and the boss of the suspension arm manifesting in the form of cracking and other material failures. Such failures can contribute to undesirable contamination due to creation of particles. Accordingly, it can be seen that there is also a need for providing a lubricant which helps to prevent the failure of contact services in a deswaging process.
It is known in the art of swaging to apply an isopropyl alcohol to members which come into contact with one another during the swaging process. Presumably, the purpose of applying the isopropyl alcohol during the process is to provide some type of lubrication among the members in contact, and then the isopropyl alcohol evaporates leaving no residue. Although a liquid lubricant of this type may have certain advantages in the swaging process, it is also known that isopropyl alcohol is not a very effective lubricant. Regardless, isopropyl alcohol applied in the swaging process does not provide lubrication in later de-swaging because the alcohol will have evaporated.
The U.S. Pat. No. 5,879,578 discloses a lubricated swage ball for use in swaging a head gimbal assembly to an actuator arm in a disk drive. The purpose of using a lubricated swage ball in this reference is to reduce transfer of aluminum oxide, or other hard materials which can be deposited on a disk during the swaging process. The swage balls are first pretreated by cleaning and then by etching to remove residual alumina from their surfaces. The cleaned, etched swage balls are then lubricated in a fluorocarbon lubricating system. Although this reference may address lubrication of a swage ball, this reference does not disclose the need to lubricate mating parts of the actuator arm and the suspension arm. Also, the inventors of the present application have learned from experimentation that swage balls may not rotate upon insertion into the through-hole, if the tolerances are sufficiently small to attain proper swaging. As a result, any lubrication is quickly scraped off by initial contact between the swage ball and side walls of the through-hole, leaving metal on metal contact.